The mechanism of enzyme-catalyzed cis to trans isomerization of maleylacetone is being studied. The role of the coenzyme, glutathione, will continue to be studied by assessing the inhibitory action of analogs of glutathione in the enzymatic reaction. The synthesis of potential irreversible inhibitors which resemble maleylacetone is being attempted. These latter compounds when synthesized should provide a labeled inhibited enzyme which could be used to identify the active site. Secondary deuterium kinetic isotope effects resulting from replacement of protium by deuterium at the isomerizing double bond of maleylacetone will be studied to gain further knowledge of the mechanism. BIBLIOGRAPHIC REFERENCE: Fumaric Acid Formation in the Diels-Alder Reaction of 2-Methylfuran and Maleic Acid. A Reexamination. W. Shih, N. Lau, and S. Seltzer, J. Org. Chem. 40, 1269 (1975).